Silicon solar photovoltaic cells are routinely produced for specialized applications such as satellite power supplies. Such cells have an efficiency on the order of 18%, but are far too expensive for economical terrestial power generation. The cells are made of single crystal silicon and their high cost is due to the large amount of single crystal silicon used in them. Only about the top 50 .mu.m of the silicon in these cells is used to generate electricity, however--the remaining 150 to 300 .mu.m being present only to serve as a supporting substrate for the top active layer. Much effort has been made to find inexpensive substrates which can be used to replace the inactive portion of the silicon, but so far these efforts have not been successful.
One of the substrates which was tried was steel, which was attractive due to its low cost. However, it was found that iron diffused from the steel into the silicon layer, rendering it ineffective. An attempt was made to prevent this diffusion by the deposition of a tungsten barrier layer in between the steel and the silicon, but iron diffusion still occurred through the grain boundaries of the very fine grained tungsten deposit.